package com.leetcode.leetcode3;

import java.util.ArrayList;
import java.util.List;

/**
 * 螺旋矩阵
 *
 * @author luhd
 * @date 2023-08-11
 */
public class Practice54 {
    /**
     * 给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。
     *
     * 输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
     * 输出：[1,2,3,6,9,8,7,4,5]
     */
    public static void main(String[] args) {
        int[][] matrix = {{1,2,3},{4,5,6},{7,8,9}};
        System.out.println(spiralOrder(matrix));
    }

    public static List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> order = new ArrayList<>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return order;
        }
        int rows = matrix.length, columns = matrix[0].length;
        boolean[][] visited = new boolean[rows][columns];
        int total = rows * columns;
        int row = 0, column = 0;
        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        int directionIndex = 0;
        for (int i = 0; i < total; i++) {
            order.add(matrix[row][column]);
            visited[row][column] = true;
            int nextRow = row + directions[directionIndex][0], nextColumn = column + directions[directionIndex][1];
            if (nextRow < 0 || nextRow >= rows || nextColumn < 0 || nextColumn >= columns || visited[nextRow][nextColumn]) {
                directionIndex = (directionIndex + 1) % 4;
            }
            row += directions[directionIndex][0];
            column += directions[directionIndex][1];
        }
        return order;
    }
}